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I was commuting to work this morning and was following a bus, suddenly I saw a huge crack, no time to steering around so just run over it. Then I felt my bike not steering properly. Pulled over and had a check I found the front tyre was complete flat. That must be from the impact because a puncture should take longer to flat a tyre. The inner tube may have exploded (haven't checked). Never MTB before so wondering is front of a bicycle takes more impact than rear? Is that why MTB has longer travel in the front?


Thanks everyone for the inputs. I have checked the front tube, there is 2-3 mm slit, so definitely from an explosion. That means the front tyre hit the crack, then deformed too much at the impact. Looking at vehicles in crashes (front ), they all have badly deformed front, rear is relatively intact. If front doesn't deform, then the force will go through all vehicle and cause even more damage to the driver. I think it's similar here.

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  • That's known as a "snake bite", often the result of running tire pressure too low. But definitely the front wheel takes more abuse than the rear. Jan 28 '16 at 13:32
  • I'm not sure that it has anything to do with it being a mountain bike, althought I do think the front wheel can take more impact. I hit a pothole once on my road bike, the front tyre lost around 50psi immediately (but didn't go completely flat). I pumped it up, rode home, and checked over the next few days - there was no puncture. The only thing I could think of was that the (presta) valve failed on impact. Maybe a similar thing happened to you?
    – PeteH
    Jan 28 '16 at 13:38
  • @PeteH that's interesting, will check after work. Jan 28 '16 at 16:33
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    Even if you don't have time to steer round it, or to brake (as in traffic braking without looking behind can be a bad idea), you almost always have time to stand up on the pedals with bent knees to absorb some of the shock. You may also have time to shift your weight backwards.
    – Chris H
    Jan 28 '16 at 16:53
  • If you can, unweight the front wheel, or bunny hop.
    – Criggie
    Jan 28 '16 at 20:25
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The principle is very similar to braking

Front wheel: when front wheel hit an obstacle, the speed of bicycle suddenly decreases. The centre of mass would shifted even more towards front wheel, making it harder to roll over an object (easier to brake). This contributes to a larger impact, comparing to the rear wheel.

Rearwheel: as weight is shifted towards the front, it is easier for the rear to roll over an obstacle. If something resist the rear to roll over, the process repeats itself (even more weight to the front).

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  • 1
    I am actually thinking the same, front wheel took most of the hit and speed slowed down and rear wheel just rolled over it. Jan 28 '16 at 12:20
  • That is why on steep downhill mtb, people shift their body all they way to the rear wheel (behind seat). Therefore, their weight wont be shifted into the front if the front hit a small obstacle by accident. Example: cdn.c.photoshelter.com/img-get/I00006RCmtnrB97I/s/860/860/…
    – Nhân Lê
    Jan 28 '16 at 12:35
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It's more likely a combination of the front wheel hitting before you had time to react properly and unweight it, and you also probably pushed down on the handlebars to shift your body back ready to do that. Even just the first could have been enough to pinch flat your tyre.

There's a whole lot of more factors, from the size and pressure of your tyres, what suspension (if any) you have, how you sit on the bike, how fast you were going and so on.

Mountain bikes have different travel balances depending on their purpose, and riding style can make a huge difference to what makes sense or what's desirable in terms of suspension travel. One factor is that it's simply easier to build a bike with huge travel in the front suspension and much harder to get the same at the back. There have been a few MTBs with an intermediate drive, for example, that runs up to a cog on the suspension pivot, allowing them tom have a longer rear swingarm and hence more travel. But if you want more travel on a front fork you just lift the headset up and have longer sliders. It's not quite that easy, but it's easier than doing the same at the back.

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  • It's a flat road and I was riding my no suspension commute bike. Thanks for the information but you haven't answered my question. Jan 28 '16 at 12:18
  • He surely has. You likely got a pinch flat. And in the situation you were describing, various factors can affect it. Based on your description, you likely hit the front wheel hard and that plus your reactions slowed you down and/or your rear wheel was properly inflated enough to not flat. Jan 28 '16 at 17:20
  • @thotwielder sorry, what is your question? I thought it was "why MTB has longer travel in the front?" You can edit your question above to make it clearer, since you seem to have got answers to four different questions so far.
    – Móż
    Jan 28 '16 at 20:19
  • @suspendeduser He didn't ask why he got a puncture. Even made the link between impact and puncture in the question. Feb 8 '16 at 11:50
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Hard-tail mountain bikes have the front suspension in order to absorb bumps and help the rider steer in a stable and predictable way. As a plus, they provide some protection on the front wheel an the inner tube. In general though, the impact is shared all around the frame. Suspension just reduces a percentage of it (depending on available travel, rebound and lock-out settings). That's why, apart from anything else, the frame geometry, helps the rider tackle the terrain designed for.

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When you hit a bump, with no avoidance maneuver, the front wheel is forced up abruptly, and most of that force is transferred to the cyclist's body. When the rear wheel later hits the same bump, at normal cycling speeds, the cyclist's body is still "up in the air" from the front wheel bump, and much less force is transmitted.

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A rider's weight is positioned behind the front wheel more compared to the rear wheel, so probably contributes to higher impact force at the front over a single crack or bump. Plus once you've lost momentum from the first impact, there's less energy for the rear wheel impact anyway.

A MTB might have more rear travel than it appears to have (smaller rear shock than front), because of the geometry of the rear linkages. A Full sus bike might well have matching travel at both front and rear but not look like it does.

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